Give packs an identity so create can refuse missing deps and load in a stable order.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/HSchool.Server/Program.cs

@@ -73,6 +73,9 @@ if (app.Configuration.GetValue("HSchool:AllowSaveReload", false))
 
     app.MapGet("/api/dev/saves-directory", (SchoolStore store) => Results.Json(new { path = store.DirectoryPath }))
         .WithName("GetSavesDirectory");
+
+    app.MapGet("/api/dev/mods-directory", (ModContent mods) => Results.Json(new { path = mods.Root }))
+        .WithName("GetModsDirectory");
 }
 
 // The realtime channel: one binary frame per protocol message, see docs/protocol.md.